Probably most HiFi users decide this comparing numbers, i.e. who offers the highest bit depth and sample rate, then comparing the numbers of available songs, and of course also the price.

As all streaming sites offer some kind of free trial, everyone can check and compare their daily performance and handling and find some issues then which may or may not annoy a user too much - for example no gapless playback on their favorite device. 

Personally I like the large catalogue of Deezer, the fact that they have almost all songs available in FLAC format and that I hardly ever haven’t found a release that interested me. Furthermore I’m not interested in more than the CD quality which Deezer offers, because I do not use a DAC, mobile device and headphones, but my computer and stereo gear.

was really hoping to spark a more passionate discussing

Maybe there will be more discussion when the U.S. users realise they can have HiFi streaming in their new Premium tier now for only one dollar more than before.  Of course there will also be the ones who do not want HiFi and have to rant about the price increase.

By the way, I forgot to mention that I really like the gapless playback in the Deezer web player now which makes listening to related albums combined with lossless streaming much more fun (complete operas, ProgRock, live). I am not sure if Tidal and Qobuz offer this either in their desktop apps or web players, but I think Apple Music does not, not sure about Amazon, certainly not with Spotify or YouTube.

As a long-time Deezer user and audiophile I've just signed up for Tidal myself. Its early days so far but i much prefer Deezer's interface, Flow (vs the very narrow playlist recommendations Tidal has been making so far) and functionality, but much of this is likely related to familiarity. However, none of these things are related to HiFi, which was your question.

Getting past familiarity and the interface, from a HiFi perspective I find Tidal to be better than Deezer, and suspect Qobuz would also be better if it was available to me (it's not). Why? Quite simply, it sounds better because HiFi is actually available to me. To be clear, with Deezer I do have a family HiFi account. I also have several audio systems and gear worth many thousands of dollars. Nevertheless I can no longer get the hifi signal to any of them and am therefore stuck with mp3 quality audio. The Android app on my phone supports HiFi, but like most phones released over the past few years it doesn't have a physical headphone jack and i have to rely on Bluetooth. I do have Sony headphones and earbuds and am able to use LDAC on the go,  but that doesn't help with my home audio gear where I can actually appreciate the difference. Two of my systems have GoogleTV devices connected to them, but the Deezer app for GoogleTV doesn't support HiFi. One of the systems has a Chromecast Audio device connected to it. However, Chromecasting hasn't worked for months now and i can't cast to any of the Google devices anymore. Two of the systems have Roku devices connected to them but Deezer's app was removed from Roku last year. It was terrible and didnt support HiFi anyway.  HEOS casting doesn't support HiFi. FireTV sticks aren't supported at all IIRC, and while I don't have a WebOS device I don't believe they support HiFi either. What's left? Connect a computer to one of them and use a web browser I suppose, but that's at all not convenient. Tidal works with all of these, and supports an impressive amount of additional gear too. It also has gapless playback and much larger playlist limits, among other things. Its also cheaper than Deezer if that's a concern.

If Deezer actually supported popular HiFi gear I'd recommend it for people looking for better sound without question. Is it stands today I'd look carefully at their supported devices page to confirm HiFi compatibility, and check with others here on this forum to confirm the devices listed still work since, for example,  Chromecast is listed as a HiFi device but doesn't work.

Qobuz is a featureless wasteland.

They don’t even have track radio (autoplay is next to useless). They have some decent curated playlists, but for me the majority of their stuff is comprised of obscure artists I’ve never even heard of. The catalog is seriously lacking and they’ve never responded to my requests to add albums.

Their mobile app runs like it’s on AOL’s dial-up in 1995, CarPlay is next to useless, and no integration with Alexa for my Echo devices.

Tidal’s recs are the epitome of stale. Daily mixes are the same rehash of songs, just in a different order. It doesn’t run well through my Echo devices at all. The app is laggy and frequently crashes. T

People joke (somewhat) about all the hip-hop recs, but it’s true.

I was gifted an annual subscription, so I gave it a fair shot. I didn’t renew.

Qobuz, deezer, and Tidal are all smaller companies, and I don’t expect them to have the resources that the big three have, and I allow that they might not have the feature set or to run as smoothly as the giants, but Qobuz and Tidal feel amateurish in comparison.

With deezer’s new pricing in the US, it’s also the least expensive.

I was with Tidal the reconditions so off base its not even funny   that said flow v1 was pretty bad tested 3 and can not wait for it to hit normal use Canada does not have quobuzz and sounds like its not worth it